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Unlike GPS and Glonass, Galileo is a civilian system. Thank you! (Ed.)

FAA: military testing could leave GPS unreliable for pilots across West in June

The Federal Aviation Administration is warning pilots that GPS testing could leave the global-positioning signals "unreliable or unavailable" across much of the West for six days in June.

The testing that began Tuesday based in Southern California could hurt flight controls for a specific kind of business jet, the FAA warned. But the testing shouldn't affect commercial airliners, according to experts.

"I think there are safeguards in place," said John Cox, a former airline pilot and now president of consulting firm Safety Operating Systems.

Pilots and air-traffic controllers will keep an eye on planes within the warning area for any flight abnormalities, he said. But if pilots hear by radio about strange GPS signals in a given area, they could adjust altitude or navigate around the problem as if it were bad weather, he said.

"You route around it as if it were thunderstorms," Cox said.

The testing centered at Naval Air Warfare Center Weapons Division based in China Lake, Calif., could affect aircraft at least 50 feet off the ground within hundreds of miles of the base to as high as 40,000 feet above sea level nearly 550 miles away. The affected area is the shape of an upside-down layer cake, with the largest layer 40,000 feet high spanning California and Nevada, and stretching across much of Oregon, Idaho, Utah and Arizona.

"This FAA flight advisory was issued in support of routine research, development, and test and evaluation efforts conducted at China Lake," the base said in a statement. "We regularly coordinate with the FAA through a standardized national process for these types of tests, which have been conducted here for more than 25 years."

China Lake, which tests weapons and avionics for tactical aircraft, encompasses 1.1 million acres, which makes it larger than Rhode Island.

The FAA alert was posted for pilots on Saturday and contained a specific warning that GPS interference could affect flight-stability controls for Embraer Phenom 300 aircraft, a type of executive jet. The FAA said pilots of those aircraft should avoid the testing area and "closely monitor flight control systems due to potential loss of GPS signal."

Embraer didn't immediately respond to a request for comment. The company's web site says 330 of the planes are flying worldwide. The planes carry six people and fly nearly 2,300 miles at up to 520 mph.

The GPS testing could be conducted from 9:30 a.m. to 3:30 p.m. Pacific daylight time on June 7, 9, 21, 23, 28 and 30. Pilots were instructed that additional alerts would be posted a day before tests, and that tests could be reduced or canceled with no notice.

Glen Winn, an instructor at the University of Southern California who worked for United and Northwest airlines, said the specific warning about the Embraer was interesting because those business jets are growing in popularity. But he said commercial airliners have enough backup systems that they shouldn't be affected.

"They alerted everyone, and that's good," Winn said. "It won't affect commercial aviation because there are so many other backup systems that are wired into the programming for the airliners."